netdev - Re: [PATCH 1/3] ifb: make device count build-time configurable

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Message-ID: <CAG-2HqUXL4zOtVR1SQTJNZcxmsYp+BiPaeZgqbsSxyGs2J8rZg@mail.gmail.com>
Date:	Tue, 12 Jan 2016 16:10:36 +0100
From:	Tom Gundersen <teg@...m.no>
To:	Lubomir Rintel <lkundrak@...sk>
Cc:	netdev <netdev@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Jamal Hadi Salim <jhs@...atatu.com>
Subject: Re: [PATCH 1/3] ifb: make device count build-time configurable

On Tue, Jan 12, 2016 at 12:56 PM, Lubomir Rintel <lkundrak@...sk> wrote:
> The devices can be created at run-time for quite some time already and the
> load-time device creation collides with attempts to create the device of
> the same name:
>
>   # rmmod ifb
>   # ip link add ifb0 type ifb
>   RTNETLINK answers: File exists
>
> This is pretty much the same situation as was with the block loop devices
> which was solved by adding a build-time configuration that the
> distributions could use as they deem fit while keeping the default for
> compatibility.
>
> Let's do that here as well.
>
> Signed-off-by: Lubomir Rintel <lkundrak@...sk>

This has been a nuisance, so would be great to see it fixed upstream.

Acked-by: Tom Gundersen <teg@...m.no>

> ---
>  drivers/net/Kconfig | 21 +++++++++++++++++----
>  drivers/net/ifb.c   |  2 +-
>  2 files changed, 18 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/net/Kconfig b/drivers/net/Kconfig
> index f184fb5..63535b4 100644
> --- a/drivers/net/Kconfig
> +++ b/drivers/net/Kconfig
> @@ -110,12 +110,25 @@ config IFB
>           This is an intermediate driver that allows sharing of
>           resources.
>           To compile this driver as a module, choose M here: the module
> -         will be called ifb.  If you want to use more than one ifb
> -         device at a time, you need to compile this driver as a module.
> -         Instead of 'ifb', the devices will then be called 'ifb0',
> -         'ifb1' etc.
> +         will be called ifb.
> +
>           Look at the iproute2 documentation directory for usage etc
>
> +config IFB_COUNT
> +        int "Number of ifb devices to pre-create at init time"
> +        depends on IFB
> +        default 3
> +        help
> +          Static number of ifb devices to be unconditionally pre-created
> +          at init time.
> +
> +          This default value can be overwritten on the kernel command
> +          line or with module-parameter ifb.numifbs.
> +
> +          The historic default is 3. If a mid-2007 version of iproute2
> +          is used (v2.6.23 or later), it can be set to 0, since needed
> +          ifb devices can be dynamically allocated via rtnetlink.
> +
>  source "drivers/net/team/Kconfig"
>
>  config MACVLAN
> diff --git a/drivers/net/ifb.c b/drivers/net/ifb.c
> index cc56fac..911af2c 100644
> --- a/drivers/net/ifb.c
> +++ b/drivers/net/ifb.c
> @@ -298,7 +298,7 @@ static struct rtnl_link_ops ifb_link_ops __read_mostly = {
>   * Note that these legacy devices have one queue.
>   * Prefer something like : ip link add ifb10 numtxqueues 8 type ifb
>   */
> -static int numifbs = 2;
> +static int numifbs = CONFIG_IFB_COUNT;
>  module_param(numifbs, int, 0);
>  MODULE_PARM_DESC(numifbs, "Number of ifb devices");
>
> --
> 2.5.0
>